'disbelieve' originates from the prefix 'dis-' meaning 'not' and the word 'believe' from Old English 'belȳfan', where 'be-' meant 'about' and 'lȳfan' meant 'to allow'.

'belȳfan' transformed into the Middle English word 'bileven', and eventually became the modern English word 'believe'. The prefix 'dis-' was added to form 'disbelieve'.

Initially, it meant 'to not allow belief', but over time it evolved into its current meaning of 'to not believe'.